Low tissue oxygen concentration or hypoxia occurs with cancer and cardiovascular disease and plays a role in diabetes and alcohol-induced liver disease. Hypoxic tumor cells are important because they resist both radiation and drug treatment. Hyperbaric oxygen, radiosensitizers, hypoxic cell cytotoxins and neutron irradiation are used to get around this resistance but hypoxia is rarely monitored so patients who might benefit are not selected and the reason for success or failure of these costly therapies is not known. The immunostaining, marker method is ideal for measuring tumor hypoxia. The marker is injected into cervix, head and neck and breast cancer patients and biopsy samples taken 24 hours later. Immunostaining of formalin-fixed, tissue sections reveals hypoxia and standard image analysis methods measure its extent. The marker method could be of enormous value in treatment planning for cancer patients and could also be used in animal studies of liver damage, stroke, cardiac arrest, diabetes, etc. PROPOSED COMMERCIAL APPLICATION: Potential commercial applications include routine use in conventional radiation therapy (potential up to 300,000 patients/year in US); in experimental therapies based on hypoxia in human tumors; in experimental models of tumor hypoxia, stroke, cardiac failure, liver disease, wound healing, angiogenesis and normal tissue development.